Olympus Mons

The largest volcano on Mars and likely the largest in the entire solar system is Olympus Mons. With a diameter of more than 500 km and a summit that towers 25 km over the surrounding plains, its volume is over 100 times that of Mauna Loa in Hawaii. Compared to other areas on Mars, there are very few craters on its slopes, indicating that it is geologically very young.

Many of the volcanoes on Mars show significant cratering, indicating that they ceased activity a billion years or more ago. By contrast, Olympus Mons is presumed to be less than 100 million years old.

Olympus Mons

This is an airbrush painting based on images from the Viking orbiters. The opening at the top of Olympus Mons is 65 km across. The clouds are water ice clouds which form in the cold, thin Martian atmosphere. These clouds are part of the evidence about the amount of water on Mars.